Step-by-step driving mechanism



June 25, 1945. J DQDDS r 2,378,987

STEP -BY- ST EP DRIVING MECHANISM Filed Sept. 21, 1943 1 j INVENTORS a Tomv MA rH/ssou 0000:,

GRAHAM JbH/v \SCOLES ATTORNEY Patented June 26, 1945 Great Britain Application September 21, 1943, Serial No. 503,275 In Great Britain August 8, 1941 2 Claims.

This invention comprises improvements in a per se known modified Geneva stop mechanism providing a step-by-step rotation of a disc or turntable, the present improvements providing positive arrest in very accurate position thereof at each step, being especially advantageous where the number of steps is large, for example twenty or thirty or more, as distinct from the usualfour or six steps in the well known Geneva and other proposed stop mechanisms wherein at each step the slotted driven disc or turntable is arrested and locked against rotation either by reason of one of its four concave surfaces being brought consecutively into engagement with a part of the notched circular periphery of the continuously rotating driving disc, the pegs on which engage consecutively in the radial slots of the driven disc to rotate the latter step-by-step or by reason of additional locking parts as described in prior British Specifications Nos. 191,- 849, 247,402, 270,181 and U. S. Patents, Nos. 719,-

198, Jan. 27, 1903, and 2,124,213, July 19, 1938,

for example.

According to the present invention a relatively large driven disc or turntable has more than six strictly radial parallel sided slots equi-angularly distributed around and extending inwards a short distance from its periphery andalso has a plurality of axially parallel pegs around its periphery, one peg only being located midway between each pair of consecutive slots, which latter are successively engaged by a single eccentric axially parallel peg on a plane-parallel relatively small continuously rotating completely circular driving disc, and the latter has cut in its face a perambulation or locus channel for accommodating, one at a time, the successive pegs on the driven disc or turntable when the driving disc, by its peg, is rotating the other disc which, during each revolution of the driving disc, is accurately held stationary by reason of the engagement with the external periphery of the driving disc at the ends of a long chord thereof of those two pegs which are on either side of the peg perambulating in said channel: the latter, for increasing the accuracy of locking, preferably has two arcuate arms passing to the periphery of the disc, by which arms the perambulating peg of the driven disc can' enter and leave, these channel arms leading to a recess, preferably circular, forming the remainder of the channel and concentric with the shaft of the driving disc.

The modified Geneva stop mechanism above set forth is particularly suitable for the wave changing arrangement of the radio receiver forming the subject of copending applications Serial Nos. 503,274 and 503,279 filed of even date herewith.

In the accompanying drawing,

Fig. 1 is a plan view of the modified Geneva stop mechanism according to the invention, showing the relatively small driving disc and a fragment of the relatively larger disc driven thereby,

Fig. 2 is a diagrammatic sectional elevation of the mechanism illustrated by Fig. 1, and

Fig. 3 is a view similar to Fig. 1, showing the driving and driven discs in difierent cooperative relation.

In Fig. 1 the driving disc I and the driven disc 2 are shown in what may be called the mid-position. The driven disc 2 has the radial slots 3, 4, 5, 6, etc. and midway between each pair of adjacent slots are' the pegs I, 8, 9, Ill, etc. There are twenty four of the slots 3, 4, etc. in this particular example.

The driving disc I is carried by the shaft the end of which is indicated at II, and is characterised on the one hand by the upstandin eccentric peg I2 which engages at each of its revolutions in one of the slots 3, 4, etc. of the disc 2 rotatable on the shaft indicated at I3, and on the other hand by the cut-away portion of its face in the form of a channel preferably comprising the central circular portion I4 into which merge symmetrically of the line passing through the axes of the shaft II and peg I2, the preferably arcuate arms I5 and I6.

It may be assumed, as shown by the arrows, that the continuously rotating driving disc I moves in the anti-clockwise direction, whilst the driven disc 2 moves step-by-step in the clockwise direction. Essentially the dimensions of the two discs and the number of slots 3, 4, etc. on the driven disc 2 and pegs l, 8, etc, are such that the pair of alternate pegs, viz. I and 9, embrace simultaneously and continuously the periphery of the driving disc I, whereby during approximately five-sixths ofthe revolution of th latter, the driven disc 2 is locked against rotation whilst in the meantime the peg 8 intermediate the peg pair I and 9 perambulates in the channel I4, I5, IB. Thus, as indicated in Fig. 3, the peg 9 (for example) has just entered the arm I5 of the channel in the driving disc I, whilst the peg 8 is just entering. from the portion I4, the arm I6 of the slot in the driving disc I, the peg I2 of the latter being engaged in the slot 5 of the driven disc 2 so as to move the latter through the small angle determined by the number of slots 3, 4, etc. and the general dimensions.

We claim:

1. A modified Geneva stop mechanism having a relatively large driven disc or turntable formed with more than six strictly radialparallel sided slots equi-angularly distributed around and extending inwards a short distance from its periphery and also having a plurality of axially par-,

allel pegs around its periphery, one peg only being located midway between each pair of consecutive slots which latter are adapted to'be successively engaged by a single eccentric axially parallel peg on a plane parallel relatively small continuously rotating completely circular driving disc, which latter has cut in its face a perambulation" channel for accommodating, one at a time, the successive pe s on the large driven disc lating in said channel.

: 2. A modified Geneva stop mechanism as claimed in claim 1, wherein the channel in the driving disc comprises a coaxial circular recess and two arcuate-arms whereby additional locking of the driven disc or turntable is provided.

JOHN MATHIESON DODDS. GRAHAM JOHN SCOLES. 

